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- TDS and extraction yield answer different questions
- Direct TDS measurements in moka coffee
- Direct extraction-yield measurements in moka coffee
- Can you calculate extraction yield from TDS alone?
- Is higher TDS better moka coffee?
- Is TDS the same as caffeine concentration?
- What does “strong moka” mean?
- How grind and recipe fit into these measurements
Quick answer
TDS and extraction yield are different measurements. TDS describes the concentration of dissolved solids in the brewed coffee; extraction yield (EY) describes extracted soluble material relative to the dry coffee used under a defined calculation. Published moka experiments illustrate both: Angeloni et al. measured 3.90 ± 0.19% TDS in one moka protocol, while Santanatoglia et al. reported moka conditions with 2.61 ± 0.01% TDS and 21.13 ± 0.90% EY, and 2.72 ± 0.02% TDS and 22.49 ± 0.51% EY. These are experimental results, not universal moka targets.
TDS and extraction yield answer different questions
Coffee discussions often use “extraction” to cover several different measurements. That shorthand becomes misleading as soon as numbers are compared.
Total dissolved solids (TDS) describes the concentration of dissolved material in the beverage. A value such as 3.90% is about the brewed liquid.
Extraction yield (EY) instead describes extracted soluble material relative to the dry coffee under a defined calculation. It requires more information than a TDS reading alone.
A third quantity can describe the extraction of one compound. For example, Angeloni et al. reported moka caffeine extraction efficiency as 10.17 ± 0.33 mg/g ground coffee. That is a caffeine result—not a 10.17% global extraction yield.
| Metric | Typical basis | Numerator | Denominator | What it tells you | What it does not tell you |
|---|---|---|---|---|---|
| TDS | % beverage | Dissolved solids | Beverage mass or equivalent analytical basis | How concentrated the brewed beverage is under the measurement method. | How much of the dry coffee was extracted by itself. |
| Global extraction yield | % of dry coffee | Extracted soluble material | Dry coffee mass | How much soluble material was recovered relative to the starting coffee under a defined equation. | Sensory quality or one compound concentration. |
| Compound extraction efficiency | mg/g ground coffee | Mass of a named compound, such as caffeine | Dry coffee mass | How much of that analyte was recovered per gram of coffee. | Total dissolved solids or global EY. |
| Beverage / grounds ratio | g/g or recipe ratio | Collected beverage or input/output quantity | Dry coffee mass or another recipe input | How the recipe/output is proportioned. | Chemical concentration unless it is measured separately. |
Direct TDS measurements in moka coffee
Angeloni and colleagues compared eight extraction methods using the same starting coffee material and measured beverage physicochemical properties alongside caffeine and chlorogenic acids. Their moka sample measured 3.90 ± 0.19% TDS.
That number is useful because the analytical basis is explicit and the method comparison is controlled. It is not a permanent specification for moka coffee. Coffee, dose, grind, water, apparatus, heat, endpoint, and collected beverage can all change the resulting concentration.
Santanatoglia and colleagues later used a documented 6-cup Bialetti Moka Express, 25 g ground coffee, and 250 g water. In one light specialty condition they reported 2.61 ± 0.01% TDS; the reported dark condition measured 2.72 ± 0.02% TDS.
The difference between those results and Angeloni’s 3.90% should not be turned into a ranking between papers. They describe different experimental systems.
Direct extraction-yield measurements in moka coffee
The Santanatoglia study is especially useful because it reports a true source-defined EY percentage alongside TDS and recipe/output metadata.
| Study / condition | Moka protocol context | TDS | Extraction yield | Output / dose context | Interpretation |
|---|---|---|---|---|---|
| Angeloni et al. (2019) | Controlled eight-method comparison; study-defined moka serving 40 mL | 3.90 ± 0.19% | Not used here as a global EY value | 40 mL study serving | Direct TDS example; compound extraction was reported separately. |
| Santanatoglia et al. (2024), light specialty condition | 6-cup Bialetti Moka Express; 25 g coffee; 250 g water | 2.61 ± 0.01% | 21.13 ± 0.90% | 202.4 ± 0.6 g output; 25 g dry coffee | TDS and source-defined EY from the same condition. |
| Santanatoglia et al. (2024), reported dark condition | 6-cup Bialetti Moka Express; 25 g coffee; 250 g water | 2.72 ± 0.02% | 22.49 ± 0.51% | 206.8 ± 3.1 g output; 25 g dry coffee | Second same-study example showing that moka has no fixed EY/TDS pair. |
The 2024 rows show why the two metrics should be presented together but not merged. A beverage can have a TDS around 2.6–2.7% while the extraction yield calculated from the experiment is around 21–22%. The percentages refer to different denominators. The same Santanatoglia dataset also underpins the separate moka pH and acidity guide, where pH and titratable acidity remain distinct from TDS and EY.
Can you calculate extraction yield from TDS alone?
No. TDS alone is insufficient.
A global extraction-yield calculation needs the mass-balance quantities and the equation appropriate to the measurement protocol. TDS tells you about the beverage concentration; it does not by itself tell you how much beverage was produced or how much dry coffee supplied those solids.
Angeloni’s 3.90% TDS cannot be converted into EY using dose or output figures from another experiment.
When comparing recipes, keep the input/output definitions explicit. The moka coffee-to-water ratio guide explains why boiler-water input, dry coffee dose, and collected beverage are separate quantities in moka brewing.
Is higher TDS better moka coffee?
Not automatically.
Higher TDS means a more concentrated beverage under the measurement method. It does not by itself say whether the coffee is balanced, pleasant, bitter, sour, aromatic, or correctly extracted for a particular preference.
Likewise, a higher extraction yield is not a universal quality score. Extraction changes which soluble material enters the beverage, while sensory response depends on the coffee, roast, concentration, temperature, and the balance of many compounds.
If the actual problem is that the cup tastes weak or watery, use the weak moka troubleshooting guide.
Is TDS the same as caffeine concentration?
No. Caffeine is one dissolved compound; TDS represents the broader dissolved-solids measurement.
Angeloni makes the distinction concrete in the same moka experiment: 3.90 ± 0.19% TDS describes dissolved-solids concentration, while 1.28 ± 0.04 mg/mL caffeine describes the concentration of one compound. These measurements use different units and cannot substitute for each other.
The dedicated moka caffeine guide separates caffeine concentration, compound extraction per gram, and caffeine per defined serving. Those values should not be used as proxies for TDS or global EY.
What does “strong moka” mean?
In analytical coffee language, “strength” is often associated with beverage concentration. In everyday use, however, someone may mean intense aroma, bitterness, roast character, body, caffeine, or simply a cup that does not taste watery.
Specify TDS, extraction yield, or compound extraction when comparing results; “strong” alone identifies none of them.
The existing weak-coffee guide starts from the sensory complaint and brew behavior. The two pages therefore answer different questions even though they meet at concentration and extraction.
How grind and recipe fit into these measurements
Grind, dose, water, heat, flow, and endpoint can influence extraction and beverage concentration.
For practical adjustments use the dedicated moka grind-size guide and coffee-to-water ratio guide. They explain basket filling, grind adjustments, and the distinction between input water and collected coffee.
Here those variables matter because they are part of the experimental context behind a reported TDS or EY value. Removing that context would make a precise number look more universal than it is.